1. Field of the Invention
The present invention relates generally to a parking brake for motorized vehicles. More particularly, the present invention relates to a simplified, durable brake system integrated into a vehicle drive axle housing whereby wheel rotation is prevented by engaging the axle ring gear with the stationary rear axle drive assembly housing.
2. Brief Description of the Background Art
Motorized vehicles, and in particular, medium-duty commercial use motorized vehicles, have an extreme need for a brake system to ensure that the vehicle will remain motionless when stopped and/or left unattended. These vehicles are typically held in position when parked by leaving their transmissions "in gear", and by the use of mechanical parking brakes. Commercial vehicles tend to require a parking brake all the more because of inherent drawbacks in their manual transmissions. Defectively designed or excessively worn dog teeth can slip, or disengage, thereby releasing the transmission gear used to hold the vehicle in position. Additionally, outside influences such as joy riders or vandals often intentionally enter a truck cab and release the extremely noticeable gear shift lever. These hazards are exacerbated by the immediate geography in which these trucks are left. These areas typically include driveways, loading docks and dump sites, each of which may be built in a slanted configuration. These grades can be substantial, which only increases the risk to life and property in the event of a run-away vehicle.
To avoid the dangers inherent in a run-away vehicle, manufacturers have developed several positive vehicle locking systems. One of the more cost efficient, and one of the most popular is known as a driveline parking brake. A driveline parking brake comprises a releaseable mechanical interlock, which attaches to the driveshaft of a vehicle to preclude the driveshaft's rotation. The brake is necessarily located behind the transmission, and the aforementioned drawbacks are of no concern, since releasing the transmission would have no effect on the driveline brake. However, these brakes are replete with their own individual disadvantages. If a propeller shaft universal joint is damaged, severed, or removed, the driveline brake is rendered useless since the vehicle can then roll even with a stationary driveshaft. Additionally, driveline brakes require constant pressure for effectiveness. This pressure is typically supplied by cable or hydraulic means. Since cable and hydraulic control systems are prone to failure, the common practice has been to bias the driveline brake system in a released position, whereby a vehicle is not stranded in the event of a breakdown. Therefore, damage to the cable or hydraulic control system automatically defeats the driveline parking brake. Further, the above deficiencies make the driveline brake useless when immobilizing a vehicle for brake or driveline maintenance.
Additional drawbacks are found in that the driveline brake system components are commonly exposed to the elements. This results in rapid deterioration through corrosion and stone damage. Frequent maintenance is required to remove accumulated dirt and debris. The cable control requires costly and frequent lubrication due to dust contamination, and penetrating moisture tends to make the cables sieze in subfreezing weather.